Bearing assemblies for gas turbines, turbochargers, and other high speed equipment are often required to withstand high rotational speeds as well as high temperatures. Such bearings are subjected to shaft whip, radial play, or sub-harmonic orbiting. Prior art devices include sleeve bearings and associated oil film provided therebetween, which films can damp some of the shaft whip. However, such devices do not always effectively deal with the shaft whip problem and, in addition, the sleeve bearings introduce undesirable friction losses into the assembly.
Preloaded ball bearing assemblies have been used in the past in such high speed equipment in order to eliminate shaft whip or orbital wobbling and axial play and to increase the accuracy of the machine. An example of such a device is reported in an article published by the Society of Automotive Engineers, Inc. entitled "Turbochargers and Turbocharged Engines," Article No. SP-442, February 1979. In that article, a rotor suspension system includes two sets of preloaded ball bearings which provide for the damping of shaft whip and additionally allow for thermal expansion caused by high speeds and hot exhaust gases without affecting the accuracy of the system.
However, this rotor suspension system does not always ensure that damping fluid is properly located between the bearings and housing thereof. Also, this device does not contain a convenient means for ensuring that lubricating fluid is metered to the ball bearings. Further, the system is not self-contained, and thus parts must be assembled separately within the high speed equipment. Such on-the-site assembly always introduces the possibilities of misassembly and contamination from the surrounding environment.
The present invention is directed to overcoming one or more of the problems as set forth above.